This invention relates generally to oil and gas well blowout prevention; more specifically, it concerns significant improvements in well blowout preventers and control systems therefor.
Well blowout preventers are constructed to close about pipe in a well in order to block upward flow or escape of well fluid at high, i.e. blowout, pressures. The pipe may desirably be rotating during such closure, and unless the preventer also rotates at the same rate, it is subject to undesirably rapid wear at the surface of engagement with the pipe, and requires replacement at frequent intervals. Attempts to resolve this problem have not provided the unusual combination of advantages in instruction, modes of operation and results as are now afforded by the present invention.